Diesel locomotive engines may utilize one or more superchargers to increase engine power by compressing ambient air to reduce its volume and increase its density. As the intake air is compressed by the supercharger, the air is heated to high temperatures. In order to reduce the temperature of the intake air and increase its density, an aftercooler is positioned downstream from the supercharger.
Tier 2 emission guidelines promulgated by the Environmental Protection Agency (EPA) set forth stringent emission standards for diesel locomotive engines. A preferred method of complying with the Tier 2 emission guidelines is to reduce intake air temperatures and thereby reduce the formation of NOx and other emissions during combustion.
Conventional locomotive cooling systems commonly use air-to-water aftercoolers, which reduce intake air temperatures only to around 180° Fahrenheit. In order to further reduce intake air temperatures, additional fans and substantially larger heat exchangers (aftercoolers and radiators) could be utilized. However, due to cost and space limitations, on locomotives, additional fans and larger heat exchangers are undesirable.
Accordingly, smaller and more efficient cooling systems capable of reducing intake air temperatures to meet EPA emission control requirements are desired.